Intracranial Aneurysms

Intracranial aneurysms are dangerous blood vessel abnormalities. The majority of individuals who suffer a spontaneous bleed from an aneurysm die from its effects.

Aneurysms are saccular out-pouchings from the wall an an artery. They form at points where arteries divide. A structural weakness in the wall of the artery allows bulging of the wall. Eventually a saccular aneurysm forms, composed of a narrow neck and bulbous sac, or fundus. Spontaneous hemorrhage (subarachnoid hemorrhage or SAH) usually occurs from the end of the fundus, producing the immediate onset of the "worst headache in my life!" Usually there is no warning prior to the hemorrhage.

Incidence

About 10/100,000 individuals will suffer a SAH each year. The incidence of hemorrhage is slightly greater  in females, twice as common among African-Americans and rises with age. Risk factors for SAH include a family history of SAH and certain disorders of connective tissue (Ehlers-Danlos, Marfan's syndrome, polycystic kidneys) . Also smoking, alcoholism and hypertension increase the risk of bleeding.    

Natural history

Patients typically complain of the abrupt onset of a severe headache, often followed by nausea, vomiting and drowsiness or coma. Neck stiffness and low back ache follow in a few days.About 5% of our population harbor unruptured aneurysms and the risk of hemorrhage is considered to be 1% to 2% per year.The risk of bleeding is less in smaller aneurysms.  Unfortunately, about 1/2 of individuals will die from SAH, usually within the first few days of rupture. A good outcome occurs in only 40% of those who survive the hemorrhage, others have lingering neurological problems.

Treatment

Management of intracranial aneurysms have challenged the ingenuity of neurosurgeons for the past one hundred years.

    Surgical clipping
       
The "gold standard" of treatment seeks to exclude the aneurysm from the circulation by placing a metal clip across its. Neck. This requires a craniotomy and the microscopic technique of a skilled surgeon. An international cooperative study a few years ago published an operative mortality of 20 to 28% (deaths occurring upto 6 months after surgery).  The outcome is heavily influenced by the condition (clinical grade) of the patient immediately prior to surgery. Patients with minimal symptoms who are alert have the lowest complication rate (11%), while comatose patients fared the worse with a 56% death rate. Good recovery occurred in 78% of alert individuals and 16% of comatose individuals.

    Hunterian ligation

        Ligation of the feeding vessel reduces blood flow to the aneurysm sac. In some cases spontaneous clotting of the sac occurs. This approach is favored in certain high risk situations. Rebleeding can occur later, as the aneurysm can fill by back filling from distal blood vessels. The technique can avoid a craniotomy as feeding vessels can be occluded in the patient's neck. It is less likely to cure the aneurysm.

    Entrapment


        This is a variation of Hunterian ligation. Both the feeding vessel and distal arteries and clipped to fully isolate the aneurysm from the circulation. This is used in some giant and fusiform aneurysms. This technique requires a craniotomy and may require a by-pass procedure to bring blood flow to distal blood vessels.

    Endovascular coil occlusion

        Endovascular techniques are growing in popularity as the technique develops. In some centers a significant proportion of aneurysms are treated by placing coils of thrombogenic wire inside the aneurysm to promote clotting of the fundus. This avoids an open operation. Complications from the procedure include stroke in a few percent of patients treated. Incomplete occlusion or aneurysm recurrence after month to years happens in 5 to 20%.

Treatment of unruptured aneurysms

    The decision to treat an unruptured aneurysm requires an understanding of the natural history of aneurysms ( i.e. the risk of no treatment) and the risks of various surgical remedies. A consensus of many published studies reveals a mortality rate of 3% and major complication rate of 7%. A recent influential multicenter study of risks published in the New England Journal of Medicine found the risk of hemorrhage in aneurysms less than 10 mm in diameter to be very low. The cumulative rupture rate was less than 0.05% in those with no history of prior hemorrhage, and 0.5% in those who had a prior hemorrhage from a second aneurysm that had been surgically treated. The rupture rate in aneurysms over 10 mm was 1% and much greater in aneurysms over 25 mm in diameter. The morbidity and mortality at one year was approximately 15%.

    All forms of treatment for intracranial aneurysms, including endovascular techniques are provided by the surgeons of the Neurosurgical Medical Clinic.